Comparação entre mapas de solos obtidos pelos métodos convencional e digital numa área complexa / Comparison between soil maps obtained by conventional and digital methods in complex area

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

16/04/2012

RESUMO

Soil maps are essential for the development of agricultural areas in an economically viable and environmentally friendly manner. So far, Brazil only has soil maps of small scale (1:250,000 to 1:1,000,000), whose use is limited to agricultural and environmental planning at the farm. Despite its importance, in Brazil a few mappings have been carried out by public authorities, primarily because budget constraints and lack of soil scientists. In addition, 5 and 6 categorical levels of the Brazilian System of Soil Classification (SiBCS), which should be used for detailed surveys, are not defined. Thus, little is known about the quality and level of similarity of the maps that have been undertaken in the country. The main reasons for this situation are: high cost, manpower and time required of mapping. An alternative to reducing these barriers is the digital soil mapping (DSM). Therefore, the objectives were to: (i) compare four conventional soil maps of the same complex area of the same scale (1:10,000), prepared by different independent soil scientists independently, and (ii) compare these with a soil map obtained by the DSM technique. For this purpose, we used a study area of 182 ha cultivated with sugar cane in the municipality of Rafard (SP). The same information was provided to the soil scientists: a geological map anda a semi-detailed pedological map (both scale 1:100,000), planialtimetric map and aerial photographs (both scale 1:10,000). Field trips, results of analysis and examination soil profiles were performed as deemed necessary. The information for the digital soil map included terrain attributes (elevation, slope, stream power, LS factor, plan and profile curvature), calculated from the digital elevation model generated based on the topographic map, and data reflectance of the surface soil of a satellite image Landsat 5 (TM sensor) obtained in the period that ground was bare. Such information has been summarized by principal component analysis, and subsequently made a subdivision of the area using Fuzzy K-means analysis. Observations were made in each compartment to classify them as a mapping unit. The maps were then compared two by two, the spatial correspondence being measured for each of the four levels established in the Brazilian System of Soil Classification, and beyond the increased textural information. Both for comparisons between conventional maps, and for comparisons to the digital map, there was a reduction of spatial correspondence to the more detailed categoric levels. The longest match final (4th level + texture) occurred between conventional maps A and B (24.3%). The highest spatial correlation in relation to the digital map that occurred was between it and the map A (35.2%) and the map B (28.7%). Therefore it is confirmed that the conventional soil maps vary according to subjective criteria of the soil scientist, whose measurement is impractical. The digital soil map generated by the proposed method achieved similar rates of correspondence with the conventional maps as those obtained among these, being a good choice in the optimization process of mapping work.

ASSUNTO(S)

agricultural management cartography mapeamento do solo cartografia planejamento agrícola remote sensing sensoriamento remoto soil mapping

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